Transcript albinism - whushguh

ALBINISM
Greer Manton, Sydney Gilbert &
Monica Starbinski
2/1/10 – Period 2
Please be respectful during this
PowerPoint. The photos you may see
today are unlike many others. Keep in
mind that they are of real people, and
you never know if someone has a person
close them that has this.
Thank You,
Sydney, Monica and Greer 
What Chromosome?
•Albinism is a genetic order, which is caused by
a gene on the ninth X (female) chromosome.
Alleles
• Alleles – an alternative form of a gene, which is
located on a specific part of a certain
chromosome.
• 2 alleles per human gene.
Recessive (aa):
-trait will only appear
if a dominant allele is
not present.
-homozygous
Dominant (AA, Aa):
-overpowers the
recessive allele.
-heterozygous
Summary Of Albinism
• Albinism – a rare, inherited, disease that you are born with,
causing a lack in pigment or melanin. Usually, the person’s
hair, eyes, and skin are affected.
• Symptoms –
Extremely light colored skin
light/white colored hair
pale blue/grey eye color, sometimes even pink
very high risk of sunburn and skin cancer
vision problems
*Interesting Facts*
There is no cure for Albinism, but precautions can be taken to
alleviate the symptoms.
- Staying out of the sun
- contacts or seeing an optician
Mode Of Inheritance
•Albinism is recessive.
• A male would have to inherit one affected X
chromosome and females would have to inherit two
affected X chromosomes to have the disorder.
• It is not dominant because you do not get it every
time, if one parent is a carrier. Both parents must
contain the gene, whether they have the disease or not.
• It is autosomal because you need two copies of the
affected gene must be present in order for albinism to
occur.
Punnett Squares
a
A
a
Aa
a
A – dominant (normal gene)
a – recessive (affected albinism gene)
A
Aa
A
aa
aa
a
A
aa
Aa
A Aa
Aa
a
a
A
Aa
Aa
Aa
Aa
Probabilty
• Ratios
1 : 2
: 1
1aa : 2Aa : 1AA
a
A
A
Aa
AA
a
aa
Aa
• Percentages
25%
:
50%
: 25%
25% aa : 50% Aa : 25%AA
Genotype and Phenotype
a
Probability
A
A
Aa
AA
a
aa
Aa
• Phenotype
-Ratios – 3 brown hair : 1 white hair
-Percentages - 75% brown hair :
25% white hair
• Genotype
- Ratios – 1AA : 2Aa : 1aa
- Percentages – 25%AA : 2Aa :aa
Key
White – Healthy
unaffected person.
May carry one
albinism gene.
Orange – Affected
with albinism, has two
of the damaged genes
Hypothetical Pedigree
Andrew
Ashley
Laura
Jonathon
Leah
George
Nick
Mary
Max
Claire
Kim
Meaning of the Albinism Punnett
Square
• AA – means that both genes are normal and they dominate.
Aa – means that one gene is normal and one is affected with
albinism. But since there is a normal gene that is dominant, it
overpowers and the person is unaffected.
aa – means that both genes are affected and the person has albinism
• Phenotype (what is SEEN)
if AA then normal brown hair is present
if Aa then normal brown hair is present but the person is a
carrier of the white hair gene
if aa then the person has white hair.
• Genotype (what is in the GENES)
AA – Homozygous Dominant
Aa – Heterozygous Dominant
aa – Homozygous Recessive
Student Practice
a
a
a
A
Genotype:
Ratio –
Percentages –
Phenotype:
Ratio –
Percentages –
Hypothetical Pedigree (Student Practice)
Key:
•Pick 2 colors.
•One for non effected
•One for affected
•Choose a Female and a
Male
•Who is married to who
•The children they have
•And probability of them
being affected.
The Rest is up to you! 
Pedigree Question and Answer:
1. How many affected parents are needed to produce
a child with albinism?
2. What are the chances that the third generation of
children will get albinism if only one child in the
second generation was affected?
3. If both parents carry the gene what’s the chance
that the child will not get albinism?